This project is directed towards elucidating the molecular basis for the expression of phosphate-regulated genes in E. coli. This will be done mainly be using genetic analyses to define the regulation of the alkaline phosphatase (phoA) gene. These studies will include: (1) genetic analysis of the phoB, phoR, and phoM regulator genes and the phoA promoter regulatory region including: (a) deletion analysis of the phoB, R region, (b) the isolation of insertion mutants of and lacZ genetic fusions to the phoB, M, and R genes, (c) construction and use of phoB, M, and R specialized transducing phage and plasmids, (d) mutation analysis of the interaction of the phoB, M, and R gene products and (e) mutation analysis of the phoA promoter-regulatory region; and (2) studies of other phosphate regulated (psi) genes in E. coli including: (a) testing the effect of phosphatase regulator mutants on expression of psi::lac fusions, (b) identification and characterization of the psi+ gene products, and (c) isolation and characterization of new mutants that affect the expression of the psi genes.